A) Field of the Invention
The present invention relates to semiconductor crystal, a light emitting device using the semiconductor crystal, and its manufacture method, and more particularly to nitride semiconductor crystal, a light emitting device using the semiconductor crystal, and its manufacture method. Nitride semiconductor is intended to mean semiconductor including mixed crystal represented by a composition formula of AlxGayIn(1-x-y)N and containing gallium nitride (GaN) as its main component and optional aluminum (AL) and indium (In) substituting for Ga.
B) Description of the Related Art
Although the performance of a light emitting diode (LED) has improved recently and its application field is broadened, the performance is desired to be improved further. The performance of a semiconductor light emitting device particularly emitting white light, is desired to be improved.
Various proposals have been made. For example, phosphor-containing resin may seal a package mounting a blue LED. Phosphor is excited by blue light to obtain pseudo white light. Alternatively, LED's of three primary colors, R (red), green (G) and blue (B), may be mounted in a package to obtain white light. When phosphor is used, there is a process of mixing phosphor in resin. If monochromatic LED's are used, mounting process becomes complicated. A white LED with simplified structure which can be manufactured through simplified process is desired.
JP-HEI-A-11-289108, which is herein incorporated by reference in its entirety, has proposed a gallium nitride based compound semiconductor light emitting device in which indium (In) is added in light emitting layer in varied composition to broaden a light emission wavelength range and emit near-white light.
JP-A-2000-286506, which is herein incorporated by reference in its entirety, has proposed a GaN based light emitting device in which a V groove is formed and then GaNAs or GaNP active layer is grown thereon to emit light having a plurality of wavelengths, enabling generation of near-white light through color mixture.
JP-A-2003-101156, which is herein incorporated by reference in its entirety, has proposed a GaN based light emitting device in which a plurality of nitride semiconductor layers having inclination angles are formed on a substrate to emit light having a plurality of wavelengths, enabling generation of near-white light through color mixture.
It is desired to realize a light emitting device capable of emitting white light having good color rendering and a light emitting device having an emission wavelength range equivalent to or near visible light range.